Is there a way to create multiple virtual copies and have lightroom automatically set the copy file name?
for example I would like to highlight a single image and create three virtual copies, one with a copy name of 4X6 another with 5X7 and the last one with 8X10.
The copy name can be changed on each copy in the metadata panel, but not the way you're requesting. If it's for a load of image, select the file, make a virtual copy. Change the copy name with the VC's still selected. Make your Auto Sync Edits in Develop. back to Grid. Make another set of VC with the VC's still selected.. repeat until you've the sets you want.
You could automate this with a script, but otherwise, it's how Sean said..